From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DAFE5C1B0D9 for ; Sat, 5 Dec 2020 20:41:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B9C7B2313A for ; Sat, 5 Dec 2020 20:41:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726893AbgLEUlc (ORCPT ); Sat, 5 Dec 2020 15:41:32 -0500 Received: from jabberwock.ucw.cz ([46.255.230.98]:36658 "EHLO jabberwock.ucw.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725601AbgLEUlc (ORCPT ); Sat, 5 Dec 2020 15:41:32 -0500 Received: by jabberwock.ucw.cz (Postfix, from userid 1017) id 506DF1C0B7C; Sat, 5 Dec 2020 21:40:50 +0100 (CET) Date: Sat, 5 Dec 2020 21:40:49 +0100 From: Pavel Machek To: Alex Belits Cc: "nitesh@redhat.com" , "frederic@kernel.org" , Prasun Kapoor , "linux-api@vger.kernel.org" , "davem@davemloft.net" , "trix@redhat.com" , "mingo@kernel.org" , "catalin.marinas@arm.com" , "rostedt@goodmis.org" , "linux-kernel@vger.kernel.org" , "peterx@redhat.com" , "tglx@linutronix.de" , "linux-arch@vger.kernel.org" , "mtosatti@redhat.com" , "will@kernel.org" , "peterz@infradead.org" , "leon@sidebranch.com" , "linux-arm-kernel@lists.infradead.org" , "pauld@redhat.com" , "netdev@vger.kernel.org" Subject: Re: [PATCH v5 0/9] "Task_isolation" mode Message-ID: <20201205204049.GA8578@amd> References: <8d887e59ca713726f4fcb25a316e1e932b02823e.camel@marvell.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="u3/rZRmxL6MmkK24" Content-Disposition: inline In-Reply-To: <8d887e59ca713726f4fcb25a316e1e932b02823e.camel@marvell.com> User-Agent: Mutt/1.5.23 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org --u3/rZRmxL6MmkK24 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > General description >=20 > This is the result of development and maintenance of task isolation > functionality that originally started based on task isolation patch > v15 and was later updated to include v16. It provided predictable > environment for userspace tasks running on arm64 processors alongside > with full-featured Linux environment. It is intended to provide > reliable interruption-free environment from the point when a userspace > task enters isolation and until the moment it leaves isolation or > receives a signal intentionally sent to it, and was successfully used > for this purpose. While CPU isolation with nohz provides an > environment that is close to this requirement, the remaining IPIs and > other disturbances keep it from being usable for tasks that require > complete predictability of CPU timing. So... what kind of guarantees does this aim to provide / what tasks it is useful for? For real time response, we have other approaches. If you want to guarantee performnace of the "isolated" task... I don't see how that works. Other tasks on the system still compete for DRAM bandwidth, caches, etc... So... what is the usecase? Pavel --=20 http://www.livejournal.com/~pavelmachek --u3/rZRmxL6MmkK24 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAl/L8FEACgkQMOfwapXb+vJE3wCfYs+cxM/a7TO3oAUetWlr1POn XBIAn3IURI08m9SC3Yh05MPaBjmvFyYq =Y8jH -----END PGP SIGNATURE----- --u3/rZRmxL6MmkK24--